Fuel control



J y 1941. MQ J. KITTLER FUEL CONTROL Filed March 3, 1939 2 Sheets-Shgetl h INVENTOR.

ton JIKiZtZer ATTORNEY.

July 29, 1941.

Fig.4. Z1

Fig.2;

M. J. KITTLER 2,250,932

FUEL CONTROL File d March 3, 1959 2 Sheets-Sheet 2 vi a N Q Q Q 7 Q Q oiN s 0 Q o U 0 s :8 s Q 0 V 5 O w I I 7 a 5 a oyz'vg 3.023.212

INVENTOR.

Milton j/fz'ZZZer BY.

ATTORNEY.

L65. #2? Per 4 I Patentea July 29, 1941 ratios at various. rates:

2,250,932 UELcoN'rBoL 'I"Milton J;- Kittler; Detroit, mic'aya signoe to'I 's'eM. I I olley and EarlHolley: I 1 J.ApplicationMarch3,1939,SerialNo.259,566 w q 6'Claims (c1. 261 37)objectiof this invention to control the mixture ratio of an airplaneengine of the variable Venturitypein which the fuel is'discharged intothe throat of a variable venturi formed between two streamlinedthrottles. In a car-;- :5 buretor of, this type, asthethrottle valves.are opened,;the: depression in the venturi decreases,

whereas in the normal type of carburetor, when the. throttle-is openedtthe depression in the the pressure of the fuel-in thefuel supply cham-7 her, so that Igcan utilize the depression. in the .15

venturilto maintain vthe mixture ratio constant when the altitude'variesand also when the load variesdueto change inqthepitch of the propel--.ler, at any given position of the variable-Venturi throttles- ,v 'Inthedrawingsz Figural showsdiagr mmatica'lly fthe preferred arrangementof. thepar-ts; a

Figure 2 shows thegdesiredp-fuel/air' mixture u e 3 shows :a' detail,being across sectional elevation taken on planefm i E? Figure!shows'a'fcross-section taken on plane H .0f i ure'3;.-."-lt Inliigure1;: ill -:is the)! aneroi'd bellows which is substantially exhausted ofair so that it can respondto variations: of pressure if a chamber 23'whieh-isconnec'ted totan air andiu'elpassage so.

-.'(which: communicates? freely with the variable aventuri) wthrough the'pas'sa'ge'" 54 so-as to --be "subjected to the depression=- inLthethrat of the t venturi formed between he throttles W3 "and 44 Thetnqws' rota-r 0 iibeef fi b d int alrriurle'ci W16 jufi stati n {515 cambe -1 51 ofair flow. measured in 2 and -44 are geareds-togeth gears45- andvli and areoperated by the" gear thus controls the. pre ure ofthe fuelln the fuel chamber-21. m a

The air chambers 26 and':26 are connected with each other'through apassage 28.-- The chambers are also connected withthe main air entrance'15 of the carburetor, communicating with the vent ring 90 through-apipe 3|. The area of a restriction-1| in the pipe 3I-thus determines thedepression in the chambers 25 and 26 andthus determines the fuel flow asthe pressure in 25 and 26 isintermediate the pressure intheairent-ra'nce l5 and-in the passage. 5

Fuel is supplied-to the diaphragm chamber 21 by anfuel pump TI-whichsupplies fuel through a ventu'ri 33 which delivers fuel to 1 the needlevalves 36-and 35.. vThe fuel supplied by the fuel pump 32 is-maintained'at a substantially constant pressure by meansof :a diaphragm bellows 36,and apressure. relief valve 31.

- As the fuel :flows through thewe'nturi as" it causes a pressure dropwhich'reflects thequanmy of fuel taken into thedia'phragm chamber 2 1.This fuel .flow causes diiierential-pre'ssure's which operate thediaphragm '36-.1ocated in' -a chamber 18*and overcome v the a spring TI;and thus moves" a- :needle "valve 39; whichv supplies fuel underpressure 1 to rthe passage? 46 which discharges into zthe zp'assagel lwhich isin free communication :with that "atmosphere through 30 theopening @9 I, and .dischargesdown the. pas

sage 42 into the throatwof thevariable venturi formed between thethrottles; 43 and M; Them-ain fuel needle valve is is moved tiththrottle 44 by means ofthe'arm 68 anfi the'ball 36 end 69. The'leve'r{66 is 'held"in contact wlth 86, which gear is integral with the cam 66:The

in eedlsvalve 29E isprovided with'tfazcentral air 1 illassage4'|.=.?which=-"supplies airifor-tidllhg t' the through the air entranceopening 48 wan-aren'- v nular" passage 446 'whichwcommunicatesizwith'the Lpassage 141 siwhenzthe throttlesare closer the needle valve; I 26acts a's a tval-ve to admit ai-r: to 'thepassagei3fli' winiaddition tothe /airifon :Inworder tofprovide Fat lean H I "ing, the manual;controlvalv'eii 6|: "is 'provid'edi. peratedbya 1ever- 52;';I?his':valve cernes'iaii oilen mg 53 and: the valve iss shownin th'elean posi v p aztionwsoathat"themort therein :is -located2:in-1 the I} o;t h e diaghraguis I 9;; and: 3 and 7-65 1 passage communicating with:the fuel; and'i'eir er iby means-pt the the fuel in the chamber 21.

- passage 36. The application of a portion of the nozzle suction asdetermined by the relative size of the restricted openings 53 and 1| totheair chambers 26 and 26 through the passage 53 regulates the fuel flowin a well known manner. The pressure in the chamber 25 adjacent to thediaphragm l6 and the chamber 26 which communicates with the chamber 25,adjacent to the diaphragm 20, regulates the relative pressure of Thismethodof regulating the pressure in the air chambers 25 and 26 is themethod that has been in use for years as the means for obtaining thelean mixture customarily used when cruising. The effect of bleeding airto the nozzle passage 36 is incidental and of no material consequence.This port communicates with the chamber 55 through the outlet 56. Thechamber 55 is also connected with the passage 24 which communicates withthe air chambers 25 and 26. The chamber 55 is bounded on either sidewith diaphragms 51 and 56 and these diaphragms .in their turn form thewalls of fuel chambers 59 and 66. These two fuel chambers communicatewith the entrance and the throat of the venturi 33, the chamber 56connecting with the throat of the venturi 53 through the passage 6|, thechamber 66 communicating with the fuel entrance 63 to the venturi 33through the passage 62.

A valve seat 66 on a bridge 61 is carried by both diaphragms 51 and 56,the bridge 51 connecting the two diaphragms 51 and 56 together andcarrying the valve seat 66 which is adapted to close the passage 56whenever the velocity of flow through the venturi 33 exceedsthe valuedetermined by a spring 12. Any increase in fuel flow through the throat33 of the small fuel venturi above the flow determined by the spring 12causes the diaphragms 51 and- 56 to move over to the left and thus movethe disc 66 and thus close high suction on the diaphragms l6 and 26. Theactual suction is determined by the relativesize of the opening 53 andof the restriction 1| in the passage 3|. large, the mixture would berelatively rich, and

if this rectriction 1| is made very small, the mixture is relativelylean. Hence the size of the restriction 1| determines the fuel economy.

As the engine ascends into the air the bellows It opens, the valve 2|rises and gradually uncovers the slotted opening 22. The nozzle suctionexisting in the chamber 23 is thus transmitted to the passage 24 so thatas the plane ascends into the air, the mixture does not become richer,despite the fall in density of the air. The characteristic of a variableventuri carburetor is such that the suction in the conduit 54 can neverbecome very slight and is always at a considerable pressure below theatmospheric pressure, but of course as the atmospheric pressure fallsthe pressure'in 54 also fails, keeping in step with the fall of theatmospheric pressure. The pressure of the atmosphere surrounding thediaphragm |6 is therefore determined by two factors: (1) the pressure ofthe atmosphere; (2) the.velocity effect of the variable venturi formedbetween the two throttles 43 and 44. The pressure in 23 is that amountbelow atmospheric pressure that is determined by the air velocity whichis determined by the throttle opening. The only time the suction in 54is slight is when operating at less than of. power, when close controlof the mixture ratio is unimportant. If the pitch of the propeller isreduced, so that the speed of the engine increases for a given throttleposition, and the flow through the variable venturi increases to such apoint that the density of the air in the throat falls appreciably, thereis again an increase of suction in the nozzle passage 36, which istransmitted to the the passage 56. Thereafter, the effect of the suc-The spring 12 unseats the valve seat 66 by moving the bridge 61 to theright, and the bridge moves to the left under the influence of the fuelflow through the venturi 33. As the valve 66 seats it is held on itsseat by the vacuum in the pipe 54, which vacuum prevents 'hunting of thevalve 66.

- The pressure of the fuel in the chamber 21 is also partiallycontrolled by the tension spring 16 which tends to draw the twodiaphragms 26, I6

' together.

Assuming that the plane is in the air having Just left the earth andflying with the valve 5| adjusted, as shown in Figure 1, inthe cruisinglean position, then as the throttles 43, 44 move to .the closedposition, an increase in suction is developed in the variable venturibetween the two throttles 43 and 44, and therefore in the passage 36.This high suction is reflected in the high suction created in the e 54which communicates through therestriction 53 through the passage 56 tothe chamber 55, and communicates chamber 23 and causes a-further openingof the slot 26 and thus causes a further reduction in the pressure inthe chambers 25 and 26 acting on the diaphragms l6 and 26, and thusstill further reduces the fuel consumption.

Thus, if the density of the air in the throat of the venturi fallseither because of an increase in altitude of a decrease in pitch, themixture remains substantially constant. As the engine approaches sixtyper cent of its rated fuel supply there comes a time when there is acritical pressure diflerential between the throat of the venturi 33 andthe approach to the venturi; At the time of this critical velocity, thespring 11 in the chamber "and the spring 12 in the chamber 56 yield, andin one case the needle 36 is opened to admit additional fuel to thepassage 46 and at the same time. the valve 66 controlling the openingleading to 56 is closed. There is thus an abrupt increase in the mixtureratio due to the lessened effect of nomle suction from the e 36 actingon the diaphragms l6 and 26 as the suction eifect acting through therestriction 53 is eliminated, and also due to the fuel admitted by theneedle valve 36.-

For all practical purposes, the manual control 53 is thereafter out ofaction until the throttles are once more closed and the fuel supplyreduced, whereupon the mixture ratio immediately and automatically goesback to the cruising lean value determined by the relative size of therestriction 53. and the restriction 1|.

The net result of these various devices is that if the-mixture ratio,Figure 2, is at A with an air flow of twenty per cent (20%) of maximumand w the D Se .24 which impos s a elatively 7 remains at the sameflgureat thepoint B when If this restriction 1| is made verythe air flow issixty per cent (60%) when it abruptly jumps to the mixture ratio C dueto the closing of the valve seat 58 on the opening leading to thepassage 56, and then as the needle 39 continues to open so as to admitmore and more fuel to the passage 40, the mixture ratio is increasedalong the line Q D. The point B at which the mixture ratio takes theabrupt jump from B to C is sixty per cent (60%) of the maximumhorsepower of the engine as air flow and horsepower are substantiallyequivalent to each other at this end of the horespower range.

If the valve II is moved, so as to disconnect the restriction 53 andcompletely block the flow through the passage M, then the mixture ratioat twenty per cent (20%) of maximum horsepower is at A andremains atthis mixture ratio until the point C is reached, at which time the valve39 opens and the mixture ratio becomes progressively richer, as shown atthe rising line C-D. The valve 39 therefore is responsible for theportion of the curve C-D and the valve 66 is responsible for the portionof the curve 3-0. The fact that this mixtureratio diagram remainsconstant at all altitudes is due to the mechanism contained in thechamber 23. This device also is responsible for the fact that thisdiagram remains unchanged regardless of any change in the pitch of thepropeller.

What I claim is:

1. In a carburetor having antair entrance, an air throttling means,adapted to form a variable Venturi passage, an air vented fuel nomedischarging into the throat of said variable venturi, said nozzle havinga restricted communication 'with the air entrance and a relativelyunrestricted fuel and air outlet into the throat of said variableventuri, a fuel supply for said carburetor comprising a fuel pumpadapted to supply fuel at a substantially constant pressure above theatmospheric pressure, a low pressure fuel supply chamber communicatingwith said pressure fuel supply, pressure reducing mechanism in saidchamber, an air chamber associated with said fuel chamber adapted tocontrol the pressure in* said fuel supply chamber, and communicatingwith the air entrance of the carburetor through a restriction, a secondair passage connecting said air chamber with said nozzle. a variablerestriction in said passage, barometric means responsive to the absolutepressure in the air vented nozzle adapted to vary said variablerestriction whereby the pressure in said air chamber associated withsaid fuel chamber is decreased as the absolute pressure in said nozzledecreases and is increased as increases.

2. A device as set forth in claim a ,restricted passage permitsadditional nozzle 1 suction to be imposed on said air chamber restrictedpassage inoperative when the fuel flow to said fuel chamber exceeds apredetermined maximum fuel flow.

3. A device as set forth in claim 1 in which a restricted passagepermits additional nozzle suction to be imposed on said air chamberthroughout the cruising range, manual means for obstructing saidrestricted passage, a pipe connecting said passage with said. airchamber, means responsive'to the fuel flow to the fuel chamber forobstructing said pipe so as to render said restricted passageinoperative when the fuel flow to said fuel chamber exceeds apredetermined maximum fuel flow.

4. In a carburetor. having a variable Venturi mixing chamber, an airentrance leading thereto, a fuel nozzle discharging into the throat ofsaid variable venturi and responsive to the air flow therethrough, afuel supply chamber connected to said fuel nozzle, an air chamberassociated with said fuel chamber and adapted to regulate the pressurein said fuel supply chamber, a restricted-passage connecting said airchamber with the air entrance, suction control means for I responsive tothe pressure in the said second air the absolute pressure therein 1 inwhich throughout the cruising range, a pipe connect-- ing said passagewith said air chamber, means responsive to the fuel flow from the fuelchamber for obstructing said pipe so as to render said chamber forcontrolling said valve means.

5. In a. carburetor having an air entrance, an air passage leadingtherefrom, a fuel supply chamber, a fuel nozzle connected thereto anddischarging into said air passage and responsive to the air flowtherethrough, an air chamber associated with said fuel supply chamberand adapted to regulate the pressure in said fuel sup ly chamber, arestricted passage connecting sai air chamber with said air entrance, aman ally operated economizer valve adapted to l pose a suction on theair chamber so as to counteract the effect of the atmospheric pressurein said air entrance, means responsive to the fuel flow into sa'id fuelchamber to render said economizer valve ineffective whenever the fuelfig; exceeds a predetermined maximum velocity 0 ow.

6. In a carburetonan air passage, a fuel supply chamber, a fuel'nozzlesupplied therefrom directly responsive to the air flow through said airpassage, a manually-operated device for restricting the fuel supply,means responsive to the rate of fuel flow for rendering said manuallyoperated device suddenly ineffective whenever the fuel flow exceeds apredetermined maximum.-

' MlLTON J. KI'I'ILER.

